Further studies on loss of T-antigen from somatic hybrids between mouse cells and SV40-transformed human cells.

The study of hybrids from three crosses between mouse cells and SV40-transformed human cells have established a positive correlation between the loss of human chromosomes and that of the SV40-induced T-antigen from the hybrid cells. These results, as well as those of other workers, provide strong support for the hypothesis of the integration of the SV40 genome in the chromosomes of transformed cells. Further, it has been shown that hybrid cells which have lost T-antigen are capable of synthesizing this antigen upon infection with SV40, thereby demonstrating that loss of the viral antigen from the hybrid cells is not due to loss of some cellular gene required for the expression of the viral genome. Results of karyological analyses of the hybrid cells argue against the existence of a single specific integration site for the SV40 genome in human cells.